The present invention relates to an information recording reproduction apparatus that records information on a magneto-optical recording medium and that reproduces the recorded information from a magneto-optical recording medium.
The development of a magneto-optical recording medium (referred to as xe2x80x9coptical diskxe2x80x9d hereinafter) is now intensive together with the recording and reproducing technique since it is a rewritable and reliable recording medium of a large storage capacity.
In a conventional magneto-optical recording reproduction apparatus, a synchronizing signal is prerecorded magnetically at the beginning of every unit of data on an optical disk together with the data. By detecting that synchronizing signal at the time of reproduction for synchronization, the subsequent recorded data can be read out sequentially.
However, when the above-described prerecorded synchronizing signal is missing in the reproduced signal according to the conventional recording/reproduction technique, there was a problem that the appropriate timing to direct a laser beam onto the optical disk for reproduction could not be established, so that data could not be reproduced reliably.
An object of the present invention is to provide an information recording/reproduction apparatus that can realize data reproduction more correctly and reliably.
Another object of the present invention is to provide a reference mark detection circuit that can detect accurately with a simple structure a reference mark such as an address mark (referred to as xe2x80x9cfine clock markxe2x80x9d hereinafter) formed together with the wobble at a groove.
According to an aspect, the object of the present invention is achieved by providing an information reproduction apparatus including an information readout circuit responsive to a supplied control signal to read out information from a mounted recording medium, a reproduction circuit demodulating information to generate reproduction data, a first period signal detection circuit detecting a first period signal from the read out information, a synchronizing signal generation circuit generating a plurality of synchronizing signals of different phases according to the detected first period signal, a second period signal detection circuit detecting a second period signal from the read out information, and a control circuit selectively supplying as a control signal to the information read out circuit a synchronizing signal out of the plurality of synchronizing signals generated by the synchronizing signal generation circuit that has a predetermined phase difference with respect to the second period signal detected by the second period signal detection circuit.
According to another aspect, the object of the present invention is achieved by providing an information recording apparatus including a data record circuit responsive to a supplied control signal to record data on a mounted recording medium, an information read out circuit for reading out information from a recording medium, a first period signal detection circuit detecting a first period signal out of the read out information, a synchronizing signal generation circuit generating a plurality of synchronizing signals of different phases according to the detected first period signal, a second period signal detection circuit detecting a second period signal from the read out information, and a control circuit selectively supplying to the data record circuit as the control signal a synchronizing signal out of the plurality of synchronizing signals generated by the synchronizing signal generation circuit that has a predetermined phase difference from the second period signal detected by the second period signal detection circuit.
According to an aspect, another object of the present invention is achieved by providing a reference mark detection circuit that detects a reference mark from a recording medium in which the plane configuration of at least one sidewall of a groove for tracking is formed so that a reference mark having a relatively abrupt second waveform of an amplitude identical to that of a relatively gentle first waveform modulated by a predetermined information signal is overlapped at a constant interval on the first waveform. The reference mark detection circuit includes a circuit generating an electrical signal having a waveform corresponding to the plane configuration of the sidewall, a circuit comparing the level of the generated electrical signal with a predetermined reference level to generate a first logic signal of a first pulse having a first duration time indicating the comparison result between the first waveform and the reference level and a second pulse having a second duration time indicating the comparison result between the second waveform and the reference level, a circuit generating a second logic signal of a third pulse having a fixed third duration time in synchronization with a leading edge of each pulse of the first logic signal, and a circuit latching the logic level of the second logic signal in synchronization with a trailing edge of each pulse of the first logic signal to output the result as a detection result of a reference mark. The third duration time is longer than the second duration time and shorter than the first duration time.
According to another aspect, another object of the present invention is achieved by providing a reference mark detection circuit that detects a reference mark from a recording medium in which the plane configuration of at least one sidewall of a groove for tracking is formed so that a reference mark having a relatively abrupt second waveform of an amplitude greater than that of a relatively gentle first waveform modulated by a predetermined information signal is overlapped at a constant interval on the first waveform. The reference mark detection circuit includes a circuit generating an electrical signal having a waveform corresponding to the plane configuration of the sidewall, a circuit comparing the level of the generated electrical signal with a first reference level that is between the peak value of the first waveform and the peak value of the second waveform to generate a first logic signal of a first pulse indicating the comparison result between the second waveform and the first reference level, a circuit comparing the level of the generated electrical signal with a second reference level that is smaller than the peak value of the first waveform to generate a second logic signal of a second pulse indicating the comparison result between the first waveform and the second reference level and a third pulse indicating the comparison result between the second waveform and the second reference level, and a circuit providing as a detection result of a reference mark a third logic signal of a fourth pulse having a leading edge in synchronization with the leading edge of the first pulse of the first logic signal and a trailing edge according to the first transition of the second logic signal subsequent to the leading edge of the first pulse.
According to a further aspect, another object of the present invention is achieved by providing a reference mark detection circuit that detects a reference mark from a recording medium in which the plane configuration of at least one sidewall of a groove for tracking is formed so that a reference mark having a relatively abrupt second waveform of an amplitude greater than that of a relatively gentle first waveform modulated by a predetermined information signal is overlapped at a constant interval on the first waveform. The reference mark detection circuit includes a circuit generating an electrical signal having a waveform corresponding to the plane configuration of the sidewall, a circuit comparing the level of the generated electrical signal with a first reference level between the peak value in the positive direction of the first waveform and the peak value in the positive direction of the second waveform to generate a first logic signal of a first pulse indicating the comparison result between the second waveform and the first reference level, a circuit comparing the level of the generated electrical signal with a second reference level that is between the peak value in the positive direction and the peak value in the negative direction of the first waveform to generate a second logic signal of a second pulse indicating the comparison result between the first waveform and the second reference level and a third pulse indicating the comparison result between the second waveform and the second reference level, a circuit comparing the level of the generated electrical signal with a third reference level between the peak value in the negative direction of the first waveform and the peak value in the negative direction of the second waveform to generate a third logic signal of a fourth pulse indicating the comparison result between the second waveform and the third reference level, a circuit generating a fourth logic signal of a fifth pulse having a leading edge in synchronization with the leading edge of the first pulse of the first logic signal and a trailing edge according to the first transition of the second logic signal subsequent to the leading edge of the first pulse, a circuit generating a fifth logic signal of a sixth pulse having a leading edge in synchronization with the leading edge of the fourth pulse of the third logic signal and a trailing edge according to the first transition of the second logic signal subsequent to the leading edge of the fourth pulse, a circuit ANDing the fourth logic signal and the fifth logic signal, and a circuit receiving the AND to generate a pulse having a predetermined duration in synchronization with respective trailing edges of the fifth and sixth pulses to output the pulse as a detection result of a reference mark. The predetermined duration is longer than the time interval between the trailing edge of the fifth else and the trailing edge of the sixth pulse.
An advantage of the present invention is that data can be recorded correctly and reliably on a recording medium and data can be reproduced therefrom.
Another advantage of the present invention is that, when an address mark is formed at a groove of a recording medium together with a wobble, the address mark can be detected at high accuracy with a simple structure.